External Reflection Fourier Transform Infrared Spectroscopy Research Articles

External Reflection FTIR Spectroscopy Applied to Archaeological Pottery: A Non-Invasive Investigation about Provenance and Firing Temperature

The mineralogical composition of archaeological pottery is closely related to the raw material and the firing conditions, thus constituting a source of information both on the origin and the manufacturing technology of ceramic artefacts. The techniques used to clarify the composition of the ceramic material from the point of view of the mineralogical phases include X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR) and petrographic analysis. Such techniques normally require the taking of a sample from the object, thus often limiting their applicability to sherds rather than intact vessels. The present study aims to investigate the possibility of applying reflection FTIR spectroscopy in the mid- and near-IR to the non-invasive analysis of the mineralogical composition of archaeological pottery, with reference to a set of Etruscan ceramic materials from the excavation of Tarquinia (Italy).

An integrated diagnostic approach to Max Ernst's painting materials in his Attirement of the Bride

Abstract The Attirement of the Bride, painted by Max Ernst in 1940, is permanently on display in the Peggy Guggenheim Collection (PGC) in Venice. Within the framework of a larger study of materials and techniques of works by Ernst at the PGC, researchers carried out a series of non-invasive analyses. A combined approach based on Vis-NIR multispectral imaging, Raman Spectroscopy, X-Ray Fluorescence (XRF), and External Reflection Fourier Transform Infrared Spectroscopy (ER-FTIR), was conducted insitu in the museum galleries. In addition, two micro-samples were analysed with SEM-EDS and μ-Raman. This approach produced vital information on the preparatory drawing, the pentimenti, the pigments, the extenders and the alteration products present in the painting. The results showed also the presence of a white preparatory layer, under the pictorial one and above the canvas, composed by lithopone (a mixture of zinc sulphide and barium sulphate), basic lead carbonate and calcium carbonate. The latter compound is probably present also as an extender. The palette included both traditional and new synthetic, commercial pigments, used as primary colours or in mixtures. Moreover, in several areas of the painting, zinc oxalates have been identified as alteration products and more rarely, zinc metal soaps, which could also be present as additives in the paint tube. These analyses revealed the masterful and innovative painting technique of this pioneer of Surrealism.

In-situ technical study of modern paintings part 1: The evolution of artistic materials and painting techniques in ten paintings from 1889 to 1940 by Alessandro Milesi (1856-1945).

A complementary multi-analytical in-situ approach has been adopted for the investigation of a corpus of ten paintings dating from 1889 and 1940 by the Venetian painter Alessandro Milesi (1856-1945), from the collection of the International Gallery of Modern Art Ca' Pesaro in Venice. Analyses were performed in situ with digital imaging, elemental and spectroscopic analysis. The analysis of pigments and binding media and their possible deterioration patterns were studied with a combination of X-Ray Fluorescence (XRF) Spectroscopy, External Reflection- Fourier Transform Infrared Spectroscopy (ER-FTIR) and Raman Spectroscopy. These analytical methods provide information regarding the evolution of the artist's palette and the painting techniques adopted in painting. Data suggest the widespread detection of zinc carboxylates, with implications for conservation and display.

Multi-analytical and non-invasive characterization of the polychromy of wall paintings at the Domus of Octavius Quartio in Pompeii

The materials and techniques of wall paintings decorating the Domus of Octavius Quartio, an outstanding patrician villa in ancient Pompeii, were investigated by means of a multi-analytical and non-invasive approach. Chemical and mineralogical characterization of pigments was obtained by the combined use of external reflection Fourier Transform infrared spectroscopy (ER-FTIR), sequentially shifted excitation Raman spectroscopy (SSR-RS) and portable X-ray fluorescence (XRF) spectroscopy. ER-FTIR and SSR-RS provided complementary molecular information for the characterization of both organic and inorganic pigments and helped to identify the pigments in the white, red, yellow, black, blue and pink paints. XRF spectroscopy provided elemental characterization of the inorganic pigments and assisted in the determination of pigment mixtures mainly constituting the green paints. Results pointed to the use of a characteristic Roman palette, consisting of calcite, cinnabar, red and yellow ochre, green earths, Egyptian blue and carbon black. A fresco application of the pigments was suggested for the execution of the wall paintings. The combined approach by spectroscopic techniques also recognized that wax had been applied as a consolidant or protective coating, and weathering products in the form of gypsum and calcium oxalate also occur.

Influence of Acyl Chain Saturation on the Membrane-Binding Activity of a Short Antimicrobial Peptide

Different bacterial types and their living environments can lead to different saturations in the chains of their membrane lipids. Such structural differences may influence the efficacy of antibiotics that target bacterial membranes. In this work, the effects of acyl chain saturation on the binding of an antimicrobial peptide G4 have been examined as a function of the packing density of lipid monolayers by combining external reflection Fourier transform infrared (ER-FTIR) spectroscopy and neutron reflection (NR) measurements. Langmuir monolayers were formed from 1,2-dipalmitoyl-sn-glycero-3-phospho-(1′-rac-glycerol) (DPPG) and 1-palmitoyl-2-oleoyl-sn-glycero-3-phospho-(1′-rac-glycerol) (POPG), respectively, with the initial surface pressures controlled at 8 and 28 mN/m. A reduction in the order of the acyl chains associated with the increase in the layer thickness upon G4 binding was revealed from ER-FTIR spectroscopy, with peptide binding reaching equilibration faster in POPG than in DPPG monolayers. Whereas the dynamic DPPG-binding process displayed a steady increase in the amide I band area, the POPG-binding process showed little change in the amide area after the initial period. The peptide amide I area from ER-FTIR spectroscopy could be linearly correlated with the adsorbed G4 amount from NR, irrespective of time, initial pressure, or chain saturation, with clearly more peptide incorporated into the DPPG monolayer. Furthermore, NR revealed that although the peptide was associated with both POPG and DPPG lipid monolayers, it was more extensively distributed in the latter, showing that acyl chain saturation clearly promoted peptide binding and structural disruption.

Determination of adsorbed species of hypophosphite electrooxidation on Ni electrode by in situ infrared with shell-isolated nanoparticle-enhanced Raman spectroscopy

Electrooxidation of hypophosphite (H2PO2−) on Ni electrode was investigated at the molecular level by external-reflection Fourier-transform infrared spectroscopy (FTIR), surface-enhanced infrared absorption spectroscopy with attenuated total reflection (ATR-SEIRAS), and shell-isolated nanoparticle-enhanced Raman spectroscopy (SHINERS). The results of external-reflection FTIR demonstrated that H2PO2− could be oxidized to HPO32− at significantly low potentials (E<−1.0V vs. SCE). ATR-SEIRAS result showed that H2PO2−ad could be adsorbed onto the Ni surface via O atoms. The adsorption orientation was further examined using SHINERS, and Ni-O stretching bands of metal-adsorbate vibration were directly detected. Comparative results of SHINERS and those obtained from the density functional theoretical calculation confirmed the adsorption orientation of H2PO2−. The present investigation verified for the first time the adsorption mechanism of H2PO2− electrooxidation on Ni surface through in situ spectroscopic data.

Evidence of coexistence of micro and nanoporosity of organo-silica polymeric films deposited on silicon by plasma deposition

A range of hybrid, SiOCH films were deposited on silicon substrates within a radio frequency plasma reactor using hexamethyldisiloxane (HMDSO) as a precursor. The plasma polymerized films were deposited at various HMDSO/argon/oxygen ratios. The composition and structure, at microscopic and nanoscopic levels, of the deposited films were determined by external reflection and transmission Fourier Transform Infrared (FTIR) spectroscopy as well as by X-Ray Photoelectron Spectroscopy (XPS). The content of carbon and oxygen in films were found to be inversely proportional to each other. XPS results showed that the outermost surface of the deposited films are nanoporous and coexist with microporosity which was revealed by electron microscopy. The structure of deposited coatings is anisotropic as was documented by polarized external reflection FTIR spectroscopy. Several correlations between the film chemical composition, surface structure, and macroscopic properties of the films such as: hydrophobicity and hydrophilicity were established.

External Reflection Fourier Transform Infrared Spectroscopy of Surfactants at the Air—Water Interface: Separation of Bulk and Adsorbed Surfactant Signals

External reflection Fourier transform infrared spectroscopy (ERFTIRS) has been used to obtain spectra of monolayers of the hydrocarbon surfactant octaethylene glycol monodecyl ether (C(10)E(8)) and the fluorocarbon surfactant ammonium perfluorononanoate (APFN) at the expanding liquid surface of an overflowing cylinder. The use of target factor analysis (TFA) to separate out the contributions of water, adsorbed surfactant, and dissolved surfactant is demonstrated. For both surfactants, there is a linear relationship between the component weight of the adsorbed surfactant, obtained by TFA, and the surface excess determined independently by ellipsometry or neutron reflection. This linear relationship suggests that the monolayers behave like isotropic films with a constant density. A sensitivity of less than 10% of a monolayer is demonstrated. The benefits of using a multivariate curve fitting procedure to analyze sets of ER-FTIR spectra are discussed and some potential pitfalls are identified. This technique is also applicable to static interfaces.

External Reflection FTIR Spectroscopy of the Cationic Surfactant Hexadecyltrimethylammonium Bromide (CTAB) on an Overflowing Cylinder

External reflection Fourier transform infrared spectroscopy (ER-FTIRS) has been used to study the adsorption of the cationic surfactant hexadecyltrimethylammonium bromide (CTAB) at the air-water interface under nonequilibrium conditions. An overflowing cylinder (OFC) was used to generate a continually expanding liquid surface with a surface age of 0.1-1 s. ER-FTIR spectra were acquired by a single bounce of p- or s-polarized radiation from the flowing surface of the OFC. The C-H stretching region of CTAB spectra was analyzed both by subtraction of a reference spectrum of pure water and by a chemometric technique known as target factor analysis (TFA). The TFA method is shown to give lower scatter in the weight of the component assignable to the adsorbed CTAB monolayer and to permit analysis of spectra at lower bulk surfactant concentrations. The surface sensitivity of ER-FTIRS is demonstrated both experimentally and by theoretical modeling. Modeling shows that surfactant adsorbed at the surface and dissolved in the bulk solution can be distinguished by reflection spectroscopy but also highlights potential errors that can arise from the neglect of the bulk surfactant contribution to the ER-FTIR spectra. Polarized spectra are consistent with an isotropic distribution of transition dipole moments of the hydrocarbon chains in CTAB. Component weights of the CTAB monolayer determined by TFA are compared with an independent determination of values of the dynamic surface excess, Gammadyn, by neutron reflection and ellipsometry. The relationship between the component weights and Gammadyn shows a small but significant deviation from linearity. Possible explanations for this deviation are discussed. The feasibility of using TFA to deconvolute ER-FTIR spectra of mixtures of hydrocarbon surfactants is demonstrated.

Structural Comparison of Langmuir−Blodgett and Spin-Coated Films of Poly(tert-butyl methacrylate) by External Reflection FTIR Spectroscopy and Two-Dimensional Correlation Analysis

The structures of Langmuir−Blodgett (LB) and spin-coated films of poly(tert-butyl methacrylate) (PtBMA) were investigated by means of external reflection Fourier transform infrared (FTIR) spectroscopy and two-dimensional correlation analysis. In addition, the structural relaxation of the films during heating was studied. At room temperature, the intensity ratio of the band at 1728 cm-1 (assigned to the CO stretching mode) and the band at 1147 cm-1 (assigned to the C−O stretching modes of the tert-butoxy group) in the external reflection infrared spectrum of the LB film was greater than that in the spectrum of the spin-coated film. However, the values of this intensity ratio for the LB and spin-coated films converged with increasing temperature. The results suggest that the structural difference between the two types of film is primarily due to strain in the tert-butoxy group in the LB film. The same trend was observed in the intensity ratio of the bands at 1255 and 1274 cm-1 assigned to the C−C−O stretching mode. Two-dimensional (2D) correlation analysis was applied to the external reflection FTIR spectral data of the LB and spin-coated films of PtBMA to analyze the relaxation of the films during heating. In the synchronous spectra of both film types, the strongest autopeak corresponded to the C−O stretching mode, appearing at 1151 and 1168 cm-1 for the LB and spin-coated films, respectively. This suggests that the conformation of the tert-butoxy group changes significantly with increasing temperature. The intensity of the autopeak at 1151 cm-1 in the synchronous 2D spectrum of the LB film is much higher than the intensities of the other autopeaks, indicating that the C−O group in the LB film undergoes mainly local reorientation, which in turn indicates that the tert-butoxy group is greatly strained in the room-temperature LB film. On the other hand, the tert-butoxy group of the spin-coated film is less strained than that of the LB film because the intensity of the autopeak at 1168 cm-1 in the synchronous 2D spectrum of the spin-coated film is slightly higher than the intensities of the other autopeaks. Furthermore, the analysis of the signs of asynchronous cross-peaks revealed that the following sequence of spectral changes is induced as the temperature increases: 1131 (bending of bbC−C−O and bbC−CO) → [1393 (CH3 bending of α-methyl), 1151 (C−O stretching)] cm-1 and 1133 → 1393 → 1168 (C−O stretching) cm-1 for the LB and spin-coated films, respectively. This suggests that in both film types the first event is associated with reorientation in both the chain backbone and the side chain. During heating, the α-methyl group relaxes along with the C−O bond in the LB film but prior to the C−O bond in the spin-coated film.

Polymerization of Poly(Itaconic Acid) on Surfaces by Atom Transfer Radical Polymerization in Aqueous Solution

ABSTRACTPoly(itaconic acid) (PIA) was grown from surface-tethered initiator sites via atom transfer radical polymerization (ATRP). The surface-tethered PIA layers were grown from hydroxyl-terminated SAMs capped with initiator molecules of 4-(chloromethyl)-benzoylchloride. This polymerization initiator molecule and a copper-based organometallic catalyst allowed tethered PIA chains to be grown via ATRP at room temperature in aqueous solutions. Ellipsometric studies and external-reflection, Fourier-transform infrared spectroscopy (ER-FTIR) confirm the presence and growth of the surface-tethered PIA layer. We describe here how changing the temperature of polymerization alters the layer growth and kinetics of the process, and demonstrate, via ER-FTIR spectroscopy, that these surface-tethered layers do bind cationic dyes through ion-exchange mechanisms.

Molecular Recognition via Hydrogen Bonding at the Air−Water Interface: An Isotherm and Fourier Transform Infrared Reflection Spectroscopy Study

Molecular recognition in Langmuir monolayers at the air−water interface as a function of headgroup orientation and substrate using isotherms and in-situ Fourier transform infrared (FT-IR) reflection spectroscopy has been investigated. Isotherm measurements show that urea and 2,4,6-triaminopyrimidine (TAP) are specifically bound to barbituric acid lipid monolayers. As expected, TAP causes a larger shift in the limiting area of the isotherms than urea due to steric requirements. The peak positions of the CH stretching vibrations of the barbituric acid lipids indicate that the alkyl chains of barbituric acid lipids 1−3 are in a close-packed all-trans conformation both before and after the recognition process. The complexation of TAP is monitored in situ using external reflection FT-IR spectroscopy through shifts of the conformation-sensitive carbonyl frequencies in the head group region, while no shifts in the carbonyl peaks are observed when urea recognizes the lipid monolayers.